Comparison of Acinetobacter calcoaceticus-baumannii Complex Identification by MALDI-TOF Mass Spectrometry and Biochemical Method, Using Whole‑genome Sequencing as the Reference Standard.

Background: Given the limited treatment options for Acinetobacter infections due to drug resistance, timely and accurate diagnosis is crucial for effective management. This study evaluated the performances of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) in identifying Acinetobacter bacteria. Methods: Retrospective forty bacterial isolates from Thailand previously identified as A. baumannii using biochemical method were recruited. The retrospective diagnostic performances of biochemical method and MALDI-TOF MS were compared, considering whole-genome sequencing (WGS) as the reference standard. Results: For identification performance, accuracy was 70% for the biochemical method, 82.5% for MALDI-TOF MS using direct colony samples, and 80% for MALDI-TOF MS using protein extract samples. In comparison to WGS, the direct colony method achieved the highest typing concordance. Regarding processing speed, MALDI-TOF MS effectively reduces the turnaround time compared to the biochemical method (p < 0.0001). Conclusion: MALDI-TOF MS significantly outperforms biochemical method in the species-level identification of Acinetobacter. The superior efficacies in terms of accuracy, resolution, and speed emphasize the technical robustness of MALDI-TOF MS and position the method as an excellent identification technique for Acinetobacter isolates.